Battery cell with small groove at surface and battery pack including the same

ABSTRACT

Disclosed herein is a battery cell including an electrode assembly of a cathode/separator/anode structure mounted in a receiving part of a battery case (cell case). The cell case is provided, at a predetermined region of the cell case corresponding to the upper end interface of the electrode assembly while the electrode assembly is mounted in the receiving part, with a small groove for pressing against the upper end of the electrode assembly to prevent the upward movement of the electrode assembly. The small groove is continuously formed in parallel with the upper end of the electrode assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 11/776,111 filed on Jul. 11, 2007, now U.S. Pat. No. 8,343,652and claims priority to Korean Patent Application No. 10-2006-0084459,filed on Sep. 4, 2004, and all the benefits accruing therefrom under 35U.S.C. §119, the disclosure of which is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a battery cell including an electrodeassembly of a cathode/separator/anode structure mounted in a receivingpart of a battery case (cell case), and, more particularly, to a batterycell constructed in a structure in which the cell case is provided, at apredetermined region of the cell case corresponding to the upper endinterface of the electrode assembly while the electrode assembly ismounted in the receiving part, with a small groove for pressing againstthe upper end of the electrode assembly to prevent the upward movementof the electrode assembly, and the small groove is continuously formedin parallel with the upper end of the electrode assembly.

BACKGROUND OF THE INVENTION

As mobile devices have been increasingly developed, and the demand forsuch mobile devices has increased, the demand for batteries has alsosharply increased as an energy source for the mobile devices. Also, muchresearch on batteries satisfying various needs has been carried out.

In terms of the shape of batteries, the demand for prismatic secondarybatteries or pouch-shaped secondary batteries, which are thin enough tobe applied to products, such as mobile phones, is very high. In terms ofthe material for batteries, the demand for lithium secondary batteries,such as lithium ion batteries and lithium ion polymer batteries, havinghigh energy density, high discharge voltage, and high output stability,is very high.

Furthermore, secondary batteries may be classified based on theconstruction of an electrode assembly having a cathode/separator/anodestructure. For example, the electrode assembly may be constructed in ajelly-roll (winding) type structure in which long-sheet type cathodesand anodes are wound while separators are disposed respectively betweenthe cathodes and the anodes, a stacking type structure in whichpluralities of cathodes and anodes having a predetermined size aresuccessively stacked one on another while separators are disposedrespectively between the cathodes and the anodes, or a stacking/foldingtype structure in which pluralities of cathodes and anodes having apredetermined size are successively stacked one on another whileseparators are disposed respectively between the cathodes and the anodesto constitute a bi-cell or a full-cell, and then the bi-cell or thefull-cell is wound.

Recently, much interest has been taken in a pouch-shaped batteryconstructed in a structure in which such a stacking or stacking/foldingtype electrode assembly is mounted in a pouch-shaped battery case madeof an aluminum laminate sheet because of low manufacturing costs, lightweight, and easy modification in shape. As a result, the use of thepouch-shaped battery has gradually increased.

FIG. 1 is an exploded perspective view typically illustrating thegeneral structure of a conventional representative pouch-shapedsecondary battery 10.

Referring to FIG. 1, the pouch-shaped secondary battery 10 includes anelectrode assembly 30, pluralities of electrode taps 40 and 50 extendingfrom the electrode assembly 30, electrode leads 60 and 70 welded to theelectrode taps 40 and 50, respectively, and a battery case 20 forreceiving the electrode assembly 30.

The electrode assembly 30 is a power generating element comprisingcathodes and anodes successively stacked one on another while separatorsare disposed respectively between the cathodes and the anodes. Theelectrode assembly 30 is constructed in a stacking structure or astacking/folding structure. The electrode taps 40 and 50 extend fromcorresponding electrode plates of the electrode assembly 30. Theelectrode leads 60 and 70 are electrically connected to the electrodetaps 40 and 50 extending from the corresponding electrode plates of theelectrode assembly 30, respectively, for example, by welding. Theelectrode leads 60 and 70 are partially exposed to the outside of thebattery case 20. To the upper and lower surfaces of the electrode leads60 and 70 is partially attached insulative film 80 for improvingsealability between the battery case 20 and the electrode leads 60 and70 and, at the same time, for securing electrical insulation between thebattery case 20 and the electrode leads 60 and 70.

The battery case 20 is made of an aluminum laminate sheet. The batterycase 20 has a space defined therein for receiving the electrode assembly30. The battery case 20 is formed generally in the shape of a pouch. Inthe case that the electrode assembly 30 is a stacking type electrodeassembly as shown in FIG. 1, the inner upper end of the battery case 20is spaced apart from the electrode assembly 30 such that the pluralityof cathode taps 40 and the plurality of anode taps 50 can be coupled tothe electrode leads 60 and 70, respectively.

FIG. 2 is an enlarged view, in section, illustrating the inner upper endof the battery case of the secondary battery shown in FIG. 1, in whichthe cathode taps are coupled to each other in a concentrated state andconnected to the cathode lead, and FIG. 3 is a front see-through viewillustrating the secondary battery of FIG. 1 in an assembled state.

Referring to these drawings, the plurality of cathode taps 40, whichextend from cathode collectors 41 of the electrode assembly 30, areconnected to one end of the cathode lead 60, for example, in the form ofa welded bunch constituted by integrally combining the cathode taps 40with each other by welding. The cathode lead 60 is sealed by the batterycase 20 while the other end 61 of the cathode lead 60 is exposed to theoutside of the battery case 20. Since the plurality of cathode taps 40are integrally combined with each other to constitute the welded bunch,the inner upper end of the battery case 20 is spaced a predetermineddistance from the upper end surface of the electrode assembly 30, andthe cathode taps 40 combined in the form of the welded bunch are bentapproximately in the shape of V. Accordingly, the coupling regionsbetween the electrode taps and the corresponding electrode leads may bereferred to as “V-form regions.”

However, such V-form regions have a problem in the aspect of safety ofthe battery. When the battery drops with the upper end of the battery,i.e., the cathode lead 60 of the battery, down, or an external physicalforce is applied to the upper end of the battery, the electrode assembly30 moves toward the inner upper end of the battery case 20, or the upperend of the battery case 20 is crushed. As a result, the anode of theelectrode assembly 30 is brought into contact with the cathode taps 42or the cathode lead 60, and therefore, short circuits may occur insidethe battery. Consequently, the safety of the battery is greatly lowered.

Accordingly, there has been proposed a secondary battery constructed ina structure in which a predetermined region of the battery casecorresponding to the upper end interface of the electrode assembly inthe battery is modified into a specific form according to the presentinvention as a solution of fundamentally solving the above-mentionedproblem.

In this connection, there has been known some technologies for forming agroove in one surface of the battery case. As an example, JapanesePatent Registration No. 3730981 discloses a secondary batteryconstructed in a structure in which a plurality of convex parts areformed at least one surface of the battery case surrounding theelectrode assembly to improve heat dissipation, and the convex parts arefilled with fillers. This technology has an advantage in that the filmsurface area of the battery case is increased by the plurality of convexparts with the result that the heat dissipation is increased, and theshape of the convex parts is stably maintained by the fillers in theconvex parts. However, it is not possible to prevent the occurrence ofan internal short circuit of the battery due to the upward movement ofthe electrode assembly when an external force is applied to theelectrode taps of the electrode assembly.

As another example, Japanese Patent Application Publication No.2001-057179 a secondary battery constructed in a structure in whichgrooves or convex parts are formed at least one surface of the batterycase in the form of an X-shape linear pattern so as to restrain theexpansion of the battery case and thus prevent the deformation of thebattery case. As clearly described in the specification of thepublication, the intersecting lines structurally serve as crossbeams toincrease the total strength of the battery case, thereby prevent thedeformation of the battery case due to the expansion of the batterycase. However, this technology has a problem in that a desired effect isaccomplished only when the linear pattern is formed in the X shape.Also, this technology has another problem in that a desired effect isaccomplished only when the battery case is a metal container, andtherefore, satisfactory results are not obtained when the battery caseis a sheet-type battery case. In addition, it is required that thelinear pattern be formed very deeply so as to structurally accomplishthe crossbeam effect. However, this process may greatly deteriorate themechanical strength of the battery case at the intersection region ofthe lines.

Consequently, there is high necessity for a technology that is capableof preventing the occurrence of a short circuit of the secondary batterydue to the movement of the electrode assembly without difficulty in amanufacturing process.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made to solve the aboveproblems, and other technical problems that have yet to be resolved.

As a result of a variety of extensive and intensive studies andexperiments to solve the problems as described above, the inventors ofthe present invention have found that, when a small groove is formed ina predetermined region of a cell case corresponding to the interfacebetween the upper end of an electrode assembly and electrode taps suchthat the small groove is continuously formed in parallel with the upperend of the electrode assembly, it is possible to prevent the upwardmovement of the electrode assembly and to prevent the occurrence of aninternal short circuit due to external impact, such as dropping, withoutdifficulty in a manufacturing process, thereby improving the safety of abattery cell. The present invention has been completed based on thesefindings.

In accordance with one aspect of the present invention, the above andother objects can be accomplished by the provision of a battery cellincluding an electrode assembly of a cathode/separator/anode structuremounted in a receiving part of a battery case (cell case), wherein thecell case is provided, at a predetermined region of the cell casecorresponding to the upper end interface of the electrode assembly whilethe electrode assembly is mounted in the receiving part, with a smallgroove for pressing against the upper end of the electrode assembly toprevent the upward movement of the electrode assembly, the small groovebeing continuously formed in parallel with the upper end of theelectrode assembly.

The occurrence of an internal short circuit of the battery due todropping of the battery or application of an external force to thebattery may act as a principal factor of explosion or combustion of thebattery. This is because, when the battery drops or an external force isapplied to the battery, the electrode assembly moves, and therefore, thecathodes and the anodes are brought into contact with each other. Highresistance heat is generated due to conducting current in the contactresistance parts. When the interior temperature of the battery exceeds acritical temperature level due to the high resistance heat, the oxidestructure of a cathode active material is collapsed, and therefore, athermal runaway phenomenon occurs. As a result, the battery may catchfire or explode.

In the battery cell according to the present invention, on the otherhand, the electrode assembly is mounted in the cell case while theelectrode assembly is stably maintained in position by virtue of thesmall groove formed at the predetermined region of the cell case.Consequently, when the battery drops or when an external force isapplied to the battery, the small groove restrains the upward movementof the electrode taps in the cell case to prevent the occurrence of theinternal short circuit of the battery, whereby the safety of the batteryis improved.

Furthermore, the small groove presses against the upper end of theelectrode assembly at the predetermined region of the cell casecorresponding to the interface between the electrode taps and theelectrode assembly. Consequently, it is possible to effectively utilizea region that does not contribute to the capacity and operation of thebattery.

Also, the small groove is continuously formed in the predeterminedregion of the cell case corresponding to the interface between theelectrode taps and the electrode assembly such that the small groove isin parallel with the upper end of the electrode assembly. Consequently,the small groove is more easily formed at the cell case than the convexparts are formed at the outer surface of the battery case or the convexparts are modified into the linear pattern, as previously described.

According to circumstances, the cell case may be also provided, at apredetermined region of the cell case corresponding to the lower endinterface of the electrode assembly while the electrode assembly ismounted in the receiving part, with another small groove such that thesmall groove is continuously formed in parallel with the lower end ofthe electrode assembly. In this case, the electrode assembly is morestably fixed in the battery case through the cooperation of theupper-end small groove and the lower-end small groove. Specifically, thesmall grooves are formed at the upper and lower end interfaces of theelectrode assembly such that the electrode assembly is stably fixed inthe receiving part of the cell case, whereby it is possible toconsiderably lower a possibility that the electrode assembly moves dueto external impact applied to the battery or the dropping of thebattery.

The electrode assembly is not particularly restricted so long as theelectrode assembly is constructed in a structure in which a plurality ofelectrode taps are connected with each other to constitute cathodes andanodes. Preferably, the electrode assembly is constructed in a stackingor stacking/folding type structure. The details of the stacking/foldingtype electrode assembly are disclosed in Korean Patent ApplicationPublication No. 2001-0082058, No. 2001-0082059, and No. 2001-0082060,which have been filed in the name of the applicant of the present patentapplication. The disclosures of the above-mentioned patent publicationsare hereby incorporated by reference as if fully set forth herein.

The depth of the small groove according to the present invention is notparticularly restricted so long as the small groove is formed in apredetermined region of the cell case corresponding to the interfacebetween the electrode taps and the electrode assembly. Preferably, thesmall groove has a depth of 0.5 to 1.5 mm

When the depth of the small groove is less than 0.5 mm, it is difficultto prevent the upward movement of the electrode assembly. When the depthof the small groove is greater than 1.5 mm, on the other hand, thebattery case may break during the formation of the small groove in thebattery case.

In a preferred embodiment, the small groove is constructed in asemicircular depression structure in vertical section. The small grooveof the semicircular depression structure restrains the breakage of thebattery case during the formation of the small groove in the batterycase. Also, the small groove structurally has high shape retention.Preferably, the small groove of the semicircular depression structurehas a radius of curvature R of 0.3 to 3 mm.

In the battery cell according to the present invention, the cell case ispreferably made of a laminate sheet including a resin layer and a metallayer. Specifically, the cell case may be a pouch-shaped caseconstructed in a structure in which a receiving part for receiving theelectrode assembly is formed in an aluminum laminate sheet. After theelectrode assembly is mounted in the receiving part, the cell case madeof the laminate sheet is sealed, for example, by thermal welding.

Preferably, the battery cell according to the present invention is alithium secondary battery. Especially, the present invention isparticularly applied to a secondary battery having an electrode assemblyimpregnated with a lithium-containing electrolyte in the form of a gel,a so-called a lithium ion polymer battery.

In accordance with another aspect of the present invention, there isprovided a battery pack including the battery cell mounted in a packcase.

Generally, the battery cell is used in the form of a battery packconstructed in a structure in which the battery cell is mounted in apack case so as to increase the mechanical strength of a cell case ofthe battery cell and to stably locate various elements at the outside ofthe battery cell.

The long and concave groove formed in the outer surface of the batterycell provides a predetermined gap when the outer surface of the batterycell is brought into contact with the inner surface of the pack case.This gap may be used as a coolant flow channel to assist the dissipationof heat from the battery cell.

In a preferred embodiment, the inner surface of the pack case isconstructed in a structure corresponding to the small groove of thebattery cell so as to reduce a possibility that a short circuit occursdue to the movement of the battery cell in the pack case. Specifically,it is possible to increase the contact force between the battery celland the pack case by forming a small protrusion corresponding to thesmall groove of the battery cell at the inner surface of the pack case.In this case, the small protrusion formed at the inner surface of thepack case is engaged in the small groove formed in the outer surface ofthe battery cell, whereby the stable attachment of the battery cell tothe pack case is guaranteed when an external force is applied to thebattery pack.

When the small groove is formed at a predetermined region of the cellcase corresponding to the lower end interface of the electrode assembly,the small protrusion may also be formed at the inner surface of the packcase such that the small protrusion corresponds to the small groove.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an exploded perspective view illustrating the generalstructure of a conventional pouch-shaped secondary battery;

FIG. 2 is an enlarged view, in section, illustrating the inner upper endof a battery case of the secondary battery shown in FIG. 1, in whichcathode taps are coupled to each other in a concentrated state andconnected to a cathode lead;

FIG. 3 is a front see-through view illustrating the secondary battery ofFIG. 1 in an assembled state;

FIG. 4 is an enlarged view, in section, illustrating the inner upper endof a battery case of a secondary battery according to a preferredembodiment of the present invention, in which cathode taps are coupledto each other in a concentrated state and connected to a cathode lead;

FIG. 5 is a front see-through view illustrating a secondary batteryaccording to a preferred embodiment of the present invention in anassembled state;

FIG. 6 is a front see-through view illustrating a secondary batteryaccording to another preferred embodiment of the present invention in anassembled state; and

FIG. 7 is an enlarged view, in section, illustrating the contact regionbetween a battery cell having a small groove formed therein and a packcase in a battery pack according to a preferred embodiment of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Now, preferred embodiments of the present invention will be described indetail with reference to the accompanying drawings. It should be noted,however, that the scope of the present invention is not limited by theillustrated embodiments.

FIG. 4 is an enlarged view, in section, illustrating the inner upper endof a battery case of a secondary battery according to a preferredembodiment of the present invention, in which cathode taps are coupledto each other in a concentrated state and connected to a cathode lead,and FIG. 5 is a front see-through view illustrating a secondary batteryconstructed in a structure in which a small groove are formed in apredetermined region of the battery case corresponding to the upper endinterface of the electrode assembly.

Referring to these drawings, the pouch-shaped secondary battery includesan electrode assembly 150 having electrode taps 140 welded to electrodeleads 120, a battery case 130 for receiving the electrode assembly 150,a small groove 110 formed in a predetermined region of the battery case130 corresponding to the interface between the upper end of theelectrode assembly 150 and the electrode taps 140.

The small groove 110 is continuously formed in parallel with the upperend of the electrode assembly 150 at the region of the battery case 130corresponding to the upper end interface of the electrode assembly 150,while the electrode assembly 150 is mounted in a receiving part 160 ofthe battery case 130, such that the small groove 110 presses against theupper end of the electrode assembly 150.

The small groove 110 is constructed approximately in a semicirculardepression structure having a radius of curvature R of 0.5 mm or more invertical section. Also, the small groove 110 has a depth of 0.5 to 1.5mm.

The electrode assembly 150 is stably maintained in position at apredetermined region of the battery case 130 by virtue of the smallgroove 110. Consequently, when the battery drops with the electrodeleads 120 down or when an external force is applied to the electrodeleads 120 of the electrode assembly 150, the small groove 110 restrainsthe upward movement of the electrode taps 140 in the battery case 130 toprevent the occurrence of a short circuit between the electrode taps 140and the electrode leads 120. In addition, the surface area of thebattery case 130 is increased by the small groove 110, and therefore,the heat dissipation characteristics of the secondary battery areimproved.

According to circumstances, as shown in FIG. 6, another small groove 112may be also continuously formed in parallel with the lower end of theelectrode assembly 150 at a predetermined region of the battery case 130corresponding to the lower end interface of the electrode assembly 150.In this case, the electrode assembly 150 is more stably fixed in thebattery case 130 through the cooperation of the upper-end small groove110 and the lower-end small groove 112.

FIG. 7 is an enlarged view, in section, illustrating the contact regionbetween a battery cell 100 having a small groove formed therein and apack case 200 in a battery pack according to a preferred embodiment ofthe present invention.

Referring to FIG. 7, the battery cell 100 has a small groove 110 formedat a predetermined region of a battery case 130 as previously described,and the pack case 200 is provided with a small protrusion 210corresponding to the small groove 110. When an external force is appliedto the battery pack, the battery cell remains stably fixed in the packcase through the engagement between the small groove 110 of the batterycell 100 and the small protrusion 210 of the pack case 200.

In a case that the small protrusion 210 is not formed at the pack case200, the battery cell 100 has a predetermined gap S defined between thebattery cell 100 and the pack case 210 due to the small groove 110. Thegap S is used as a kind of coolant flow channel to assist thedissipation of heat from the battery cell 100.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

As apparent from the above description, the battery cell according tothe present invention has the effect of restraining the upward movementof the electrode taps to prevent the occurrence of an internal shortcircuit of the battery cell when the battery cell drops or when externalimpact are applied to the battery cell, whereby the safety of thebattery cell is further improved.

What is claimed is:
 1. A battery pack comprising: a battery cellincluding an electrode assembly of a cathode/separator/anode structure;a cell case having a receiving part for housing the battery cell, thecell case being in contact with the battery cell; and a pack case formedabout the cell case; wherein the cell case that is made of a laminatesheet including a resin layer and a metal layer is provided, at apredetermined region of the cell case corresponding to an upper endinterface of the electrode assembly while the electrode assembly ismounted in the receiving part, with a small groove adjacent electrodetaps for pressing against the upper end of the electrode assembly toprevent an upward movement of the electrode assembly and stably maintainthe electrode assembly in position when an external force is appliedthereto, the small groove continuously extending along and being inparallel with the upper end of the electrode assembly, wherein an innersurface of the cell case is protruded toward the upper end interface ofthe electrode assembly to form the small groove, and wherein the batterypack has a coolant flow channel defined by the small groove between thebattery cell and the inner surface of the pack case.
 2. The battery packaccording to claim 1, wherein the cell case is also provided, at apredetermined region of the cell case corresponding to the lower endinterface of the electrode assembly while the electrode assembly ismounted in the receiving part, with another small groove such that thesmall groove is continuously formed in parallel with the lower end ofthe electrode assembly.
 3. The battery pack according to claim 1,wherein the small groove has a depth of 0.5 to 1.5 mm.
 4. The batterypack according to claim 1, wherein the small groove is constructed in asemicircular depression structure in vertical section.
 5. The batterypack according to claim 4, wherein the small groove of the semicirculardepression structure has a radius of curvature R of 0.3 to 3 mm.
 6. Thebattery pack according to claim 1, wherein the battery cell is a lithiumsecondary battery.
 7. The battery pack according to claim 1, wherein thebattery cell is a pouch-shaped battery cell.